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The dynamic stability of dense medium suspension is the premise to ensure the effective separation of mineral particles in the separation equipment. It is usually difficult to directly measure the dynamic stability of the suspension in the separation process of the dense medium cyclone. In this paper, a parameter defined as the density difference value between the underflow and overflow of cyclone is used to characterize the dynamic stability of the suspension in the separation process. Under the conditions of different operating parameters and structural parameters, the influencing factors of the dynamic stability of 1.30–1.60 g/cm3 dense medium suspension are systematically studied. The results show that the parameter value is in the range of 0.20–0.50 g/cm3, which is conducive to the separation of particles. When the suspension density increases, the characteristic value of density difference decreases, the influence of the suspension density, feed pressure, the diameter of underflow and overflow port diameter on the density difference characteristic are also researched. Eventually, the formula for calculating the density difference of the characteristic value of suspension is derived. [ABSTRACT FROM AUTHOR]

Separation mechanism of liquid-solid fluidized bed separator (LSFBS) was studied by using theoretical analysis and experimental researches.Characteristics of autogenous medium fluidized bed in LSFBS were analyzed and the influence of autogenous medium size on the separation performance of LSFBS was studied,taking quartz particles of various sizes as autogenous medium.According to the separation results,a better segregation could be achieved by using finer autogenous medium.Particularly,the optimum of Ep value of 0.15~0.2 mm quartz was 0.053 while that of 0.25~0.45 mm quartz increased to 0.095.Finally,the influence of size distribution of feed and operating conditions on the separation efficiency was analyzed.Reducing feed size range and enlarging lower-size limit of feed could improve the device performance.Under a certain bed pressure,a smaller upward current velocity could generate a higher solid volume fraction and bed effective density.A smaller upward current velocity could also decrease the influence of size and shape on the movement of particles.All of these changes could induce a better separation performance for LSFBS.

Water velocity and bed density are most important operating variables affecting the separation of coal particles in Teeter Bed Separator (TBS). In this paper, experimental investigation is carried out to evaluate the matching effect of operating variables on the performance of TBS for separating a coal sample with size of 1–0.25 mm. Furthermore, the particle motion based on the Euler-Euler simulation approach and slip velocity model is analyzed to explain the experiment phenomenon. Experiment results show that at a constant cut density (δ50), two operating variables present a negative relationship. When a considerable clean coal yield is produced, the matching of a lower water velocity with higher bed density displays more desirable performance. The performance difference at different matching operation is also reflected in the separation of narrow size particles. The simulation results and theoretical analysis on particle motion illustrate that coal particles are separated more significantly according to their density at the operating condition of lower water velocity matching higher bed density. The study is of great importance to offer the reference of operating variables controlling and develop numerical simulation study for TBS. [ABSTRACT FROM AUTHOR]

In this study, the −1 mm fine coal is treated in a laboratory Knelson concentrator. The influence of various parameters (e.g., feed rate, solid content, centrifugal force, and the fluidization water pressure) on the yield and ash content of clean coal are thoroughly investigated and estimated by statistical polynomial models obtained using the response surface method (RSM). A second order polynomial model is developed to predict the yield and ash content; the models have a correlation coefficient of 0.9902 for yield and of 0.9221 for ash content of clean coal. Three-dimensional plots are presented to show the effects of process variables and their interactions on the response variables. The results show that all the variables affect the yield and ash content of clean coal to some degree. However, the centrifugal force and fluidization water pressure are found to be the most significant factors. Additionally, a numerical optimization process was applied to the developed models to search the factor space for the best trade-offs to achieve the maximum yield and lower ash content in the range of the experimental data. Under optimized working conditions, good separation efficiency is obtained with probability error Ep of 0.09. [ABSTRACT FROM AUTHOR]

The separation of fine coal in a laboratory Knelson concentrator was studied through experimental and numerical simulation. The flow field characterized of Kenlson concentrator simulated in a three-dimension laboratory Knelson concentrator by using CFD modeling. The results show that the flow regime can be treated as laminar flow, which propitious to layering for particles. In the riffle part, eddies were created by the rotational flow and fluidizing water. The flow of fluids changes from turbulence to laminar, which was propitious to separation for particles. So, the separation processes were realized in riffle part. The CFD-DEM modeling was applied for the first time in the study of the influence of centrifugal force and fluidizing water rates on the separation performance of a laboratory Knelson concentrator. The simulation results indicate that the Ep value was increased with decreasing the centrifugal force at the constant fluidization water rates, and increased with increasing the fluidization water rates at the constant centrifugal force. The simulation results were consistent with the experimental results and the CFE-DEM model was effective and reliable. [ABSTRACT FROM AUTHOR]

To enhance low-rank coal flotation efficiency, dibutyl phthalate (DBP) and cetyltrimethylammonium bromide (CTAB) were used as collectors, respectively. The adsorption selectivity performance of CTAB and DBP on coal samples with different densities were characterized by the total organic carbon content, contact angle, and Fourier-transform infrared spectra. The results indicate that both DBP and CTAB greatly improved flotation yield compared with diesel, but only DBP can yield a concentrate with a low ash content. DBP had a higher adsorption capacity and bestowed a greater change in contact angle for low-density coal, while CTAB followed the opposite behavior. Furthermore, the ester group of DBP consumed the oxygen-bearing functional group and increased the alkane chain content on the coal surface, leading to a noticeable increase in hydrophobicity of the low-density coal sample. [ABSTRACT FROM AUTHOR]

Separation tests on a high-sulfur-coal sample were carried out using a water-only cyclone (WOC) with a three-stage cone (also named a tri-cone water-only cyclone). The lower size limits of deashing and desulfurization were determined to be 0.098 mm and 0.045 mm, respectively. According to a float-and-sink analysis of various size fractions in the overflow and underflow, the Ecart probable (Ep) value as well as the separation density increased as the lower size fractions decreased. According to dynamic analysis, terminal hindered-settling velocities of spherical particles in the radial direction were obtained and an equation to estimate the lower removal size limits of heavy minerals was developed. With the help of numerical simulations of water–air two-phase flow fields in a tri-cone water-only cyclone (TWOC) and a conventional hydrocyclone, the role of the three-stage cone in the separation process was analyzed. [ABSTRACT FROM AUTHOR]

In order to improve the adaptability of air dense medium fluidized bed on different coal moisture, the hot air was blown to the fluidized bed instead of the air at ordinary temperature, so the lignite can be separated efficiently. The effects of drying temperature, drying time and air flow in fluidized bed were investigated with ecart probable moyen Ep. The results showed that when the drying temperature ranged from 30 °C to 50 ²C, the higher the drying temperature, the lower the value of Ep. When the drying time were between 1 minute and 5 minutes, the longer the drying time, the lower the value of Ep, and Ep decreased slowly after drying 3 minutes. When the air speed were between 8 m³/h and 12 m³/h, Ep reduced first, then rose with air speed increased. The higher surface moisture of the coal sample, the more significant influence of drying temperature and time, air volume on Ep. The Ep was 0.022 g/cm³ when the drying temperature was 50 ²C, the drying time was 5 minutes, and the air flow for coal sample of 1% surface moisture were 10 m³/h. [ABSTRACT FROM AUTHOR]